1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a microfluidic device, and more particularly, to a microfluidic device including two bonded sheets and a method of fabricating the microfluidic device.
2. Description of the Related Art
Microfluidic devices are used to perform biological or chemical reactions by operating a small amount of fluid. A related art microfluidic device includes a microfluidic structure formed in a platform, for example, a chip or a disk. The microfluidic structure includes a chamber that can store a fluid, a channel, through which the fluid can flow, or a valve that may adjust the flow of the fluid. The chamber, the channel, or the valve may be formed in the platform in various combinations.
A bio chip is formed by disposing a microfluidic structure on a chip so that tests including biochemical reactions can be performed on a small size of the chip. In particular, a device for performing a plurality of processes and operations on one chip is referred to as a lab-on-a-chip.
In order to transport the fluid in the microfluidic structure, a driving pressure is required. A capillary pressure or a pressure generated by an additional pump may be used as the driving pressure. Recently, centrifugal force-based microfluidic devices, wherein a microfluidic structure is placed on a rotating platform formed as a compact disk, have been suggested. The above centrifugal force-based microfluidic device is referred to as a Lab CD or a Lab-on-a-CD.
A related art method of fabricating a microfluidic device includes a process of engraving a surface of at least one of two substrates to form a microfluidic structure, and a process of bonding the two substrates to each other so as to enclose the microfluidic structure. The two substrates can be bonded to each other using a thermal bonding method, a solvent bonding method, an ultrasonic welding method, a laser welding method, or an adhesive bonding method.
U.S. Pat. No. 5,599,411 discloses a method of fabricating a microfluidic device using ultrasonic welding. However, in the ultrasonic welding method, a reagent in a liquid state may vaporize or degenerate since a strong energy of the ultrasonic waves is transferred to the entire platform, and thus, this method cannot be used to fabricate a microfluidic device by bonding two substrates after distributing a liquid reagent into a chamber. The thermal bonding method or the laser welding method require a high temperature or a high energy condition, and thus, it is difficult to use them to manufacture a microfluidic device including two substrates.
On the other hand, US patent application No. 2004/0241381 discloses a method of forming grooves for receiving an adhesive around a chamber or a channel of a lower substrate, and injecting a liquid adhesive into the grooves to bond an upper substrate and the lower substrate 12 to each other. However, according to this method, since the liquid adhesive should fully fill the grooves, a large amount of liquid adhesive is required. In addition, the liquid adhesive may overflow in the chamber or the channel from the grooves, thereby closing fine channels. Also, bonding reliability is degraded due to air bubbles formed on bonding surfaces of the two substrates, and accordingly, the fluid received in the chamber or the channel may leak.